Well, honestly, I think the pose does nothing to add to the effect here. In my opinion, the girl in the back is the "model" one, and he one in front is less photogenic. There's something that the girl in the back has got and that the girl in the front lacks. The idea of two young,beautiful women in one photo is an ages-old concept, but the way it's been done here is not coming together into a well-conceived photograph. The front model's leg positioning looks awkward...the girl behind her is not shown well.
The tarp is extremely distracting. Okay, to offer an idea; there are two "frames" in this picture, the bottom and the top frames, so you could have positioned the girl with the best legs seated to the left side of the bottom frame, with her butt on the left side,with her legs pointed to the right of the frame. Then, take the other model and have her stand on the right hand side
of the frame, facing the other girl,and maybe "hanging onto" the tarp..If you can;t or couldn't get the tarp out of the frame, I understand, but if it is going to be in the frame, you might as well have the standing model relate to it, or use it as a prop.